Electric fuse



July 25, 1933. F. N CONAN-r 1,919,274

ELECTRIC FUSE Filed sept. 27, 195o fffff l l l 1 fnverzor:

Patented July 25,

UNITED STATES PATENT oFl-ICE CHASE-SHAWIUT OFTNEWBURYPORT, MASSACHUSETTS, A CORPORATION OE MASSACHUSETTS ELECTRIC FUSE Application led September 27, 1930. Serial No. 484,851.

. This invention relates to electric fuses and especially thosewherein the fusible element can be renewed.

The fuse withwhich the present invention is more particularly concerned lcomprises `a tubular insulating casing having external screw threads formed on the end thereof, with a thin metal shell or ferrule having complelmental eXternal'and internal screw threads received on the s crewthreads of the casing and havin screw threaded thereon an end cap or equivalent clamping or holding mem'- ber for the fusible element which is located within the casing.

' One of the objects of the present invention is the provision of improved meansvwhich, in combination with the inter-engaged screw threads of the shell and casing, locks the shell to the vcasing against rotation on the screw threads of the casing.

Another object of the invention is the provision of arl-external annular groove in the casing between the body and the screw threaded portion thereof'into which a part -of the metal shell is located so as to. engage the walls of the groove and thereby hold the f shell against axial displacement and thereby against rotation on the screw threads of the urther object of the present invention is the provision of venting means for the interior of the casing which includes a venting channel that passes under the metal shell and is open to the atmosphere at or `near the inner end of the shell, so that the metal vapors need `not vent between thescrew threads of the shell and end cap, as has been ,the case in some instances heretofore, with the resultthat thev shell and en cap have become Aso strongly bonded together as to render removal of the end cap diicult. l

` A yet further object is the provision of a fuse having a screw threaded casing provided with a generally axially-extended vent passagewhich cuts through the screw threads to a pointslightly below' the roots thereof, and

a metal cap-holding ferrule screw threaded on the screw threaded portion of the casing over the vent passage and with a part of its internal screw threads forming a wall of the vent passage. v

Another object of the invention is the provision of a fuse having a vent passage that has a plurality of enlarged chambers with restricted channels connecting them in series so that the gas can expand in each of the chambers in succession and therebv be sub-- close to, the bottom of the vent passage so as to provide the aforesaid enlarged chambers and restricted. interconnecting channels, the metal shell also constituting an effective coolingand heat-dissipating agent for the heated gases that are expelled from the casing through said passage.

A further object is generally to improve the construction and operation of electric fuses.

It has been found that when the shell and other thin-section parts. that are subject to the arc vapors are made of a metal as brass,

, they can become burned by the hot vapors, but `that when these parts are made of steel or some material having a melting temperature higher than the vaporizing temperature of the material of the fusible element, they are immune from burning; and this constitutes a further obj ect of the-invention.

Fig. 1 is a side view of the electric fuse embodying the present invention.

Fig. 2 is a sectional view taken along line '2 2 of rig. 1.

Fig. 3 is an end view of the casing of Fig. 2.

Fig. 4 is an enlarged sectional detail of one end of the fuse casing.

Fig. 5 is a section taken along line 5 5 of Fig. 4. A

Fig. 6 is a sectional detail taken along line 6 6 of Fig. 4.

Fig. 7 is a sectional detail taken along line 7 7 of Figy. A

The electric fuse herein shown as embodyportion. The end 16 of th transverseend' p 65: than. the 'diam ter ing the presept invention com rises a tubular enclosing casing 10 formed o insulating material, as, fiber. The casing is provided w1l an end portion 12 which has adiameter that A. is somewhat less than the external diameter of the body portion of the casix, and has ex.-

ternal screw `threads 14 form in said end e casing-1s sm on its outer periphery and extends beyond the `end ofthe screw threads and has an ex-l terior diameterl sli tly less than the diameter ofthe roots o the screwl threads.' An .anniatzdgroove- 18 havin a rounded bottom 4isl between the y of the casi and the screw threaded portion thereof aillqhas. a diameter at thebottom approximately ual to the-diar'neterof the smooth end portion of thencasing. A thin walled metal shell or ferrule 20 is received on the screw threaded ,portion of the casing. The shell is provided withjinternal s crew threads 22 whic engage theexvternal screw threads of the casing and is-al's'iprovidedrwith external screw threads y '24. e internal and external screw threads are complemental and are formed b rolling the threads into the shell ina we known .-manner. The inner en of the shell is` ro vided with ah annular neck 26 which is ro led into the annular groove 18 and intointiinateV en mentlwithvthe of the ve, after the shell has been'screw three ed onl "ther casing so that the neck locks the shell pel'- 'lma'nently against axial. 'displacement in either. direction on the casing and-'thereby prevents fromvbeing'rotated-to'any deleterious lextent on the screw threads. ectinwardl fromthe shell linto themate A'of the-casmg-to hold the shellaglin'st rotation alth not essential. A metal tube is fitted within` theshellnnder'the screw threaded pork:tionthereof and-'is secured in place by rivets 1 "32. 'Said-tubejs rovidedwith an'mtegral youd the bod i ofthe shell 'and overlies the end ofthe tu ular The end'wall'is provided with a semicircular "aperture 86 t l therein which has a flat fuse supportingle'dg'e A fusible element or link 40'is extended through the lcasin and has its outer end 42 --nal exten edthroug h` e *over and in contact wi the end wail. 84; metnl'end cap 414'is screw threadedupon;the-xv casing,`andhas internal'screwthreads'4`6 that thereof, is provided withza'n emular portion ooth 36:

16 channels 52 located at each end of. lSaid channels extendaxialliof the` `1n hthespursare' ular 84 which outstands be f engagefthe-externalecrewthreads 24 ofthe;Av L t .Shellfoldf' 011111011 481m] f ,f l

'foroes'the retlexedendof the-against,v v thewalltandfthereby retainsthe fuse in Mod-159i; i.

the fuse casin toprovideavent' therebetween.g The end wall 48nd? 51eend th cap outstands4 from theend wall 34 ofthe y fuse casing by the thickness of the end 42 ofv the fusible element and thus provides a venting space which -is in communication with the interior of the through the opening In accordance .with this invention improved means are provided to permit the escape of the high pressure and vapors formed withint e mterionzo ,the casing when the fusible element blows and to cool ldzhe prior to their liberation into the atmosphere. To this end the .fuseis provided `with o ne 'or more, and as hereshown fourgenftigeg tal ` casing', on the exterior t ereof', from they#` u ced end rtio'n-l throughthe :screw .l. threaded'portlon 12 and transversely' through the screwl threads-14 thereof andthrough and across the annular groove 18 into'thel body portion of the casing where they have open- A' ings 54 at thesurface of the body portion tlliltare 'so arranged that the gases are' disc r wid ofthe slots can be vn .nyth emredf awidthof approximately one-e' th.' of en inch giving good-results. The 56 of the 'groove isparallel withtheaxis of the Andis-,8.11853 below *the-roots. of the screwthreads 12'an issubstantially in line with the, ripheral surface of the end shell'20. .and-the shell 'fqrms'tM'wp-,g'n o( sie laterally away from-th@ .The

lil

outlets of the channels. The arrangement .of the series of expansion chambers and the small passages 60 that connect them consti-v I tute means which reduces the iiow ofthe through thel channels and thus permits f t e channels to be wide so that they will not leusrteadily clogged by accumulation of metal In further accordance with this'inventionthe thin threaded ferrule in particular,l

and preferably also the tube and other thin parts that are subject to the hot fuse vapors 'are composed of somematerial that has a melting temperature higher than the vaporicing temperature of themetal of the fusible element 40, since this vaporizing temperature is substantially the tem rature of the arc v vapors. Thus the meta parts will not beto the cooling e'ect of the-,air and also since l golias a.relatively thick and heat-absorbent A fuse having an externall screw threaded casing and an internally an externally thin metal cap holding shell f is described land claimed in my co-'pending application Serial No. 316,210, iledOctober 31, 1928.

' I claim: V

1. An electric fuse having an enclosing casing, an internally screw threaded metal shell on vthe end of the casing, a fuse engaging member carried by the metal shell, and a venting passage which communicates with the interiorof said casing and passes between `said casing and said shell and traverses the internal screw threads of said lshell and has an outlet at the exterior of said casing.

.2. An electric fuse having an externally screw-threaded enclosing casing, an internally screw-threaded metal shell on the end of the casing and the external screw threads thereof, a fuse engaging member engaged with said shell, and a venting passage in said casing which is in communication with the in terior of said casing and which traverses said screw threads and passes betweenl said. shell and casing and has an outlet exteriorly of /ss e s the casing' beyondsaid shell.

3. An electricffuse -having an enclosing casing, an internally screw-threaded Vmetal' it fand said casing and tra'verses said screw` threads and has an opening exteriorlyof the casing.

4. An electric fuse having an enclosingcas ing, an internally screw-threaded metal shell on the end of said casing, a fuse `engaging member engaged with said shell, and a venting passage which is in communication with the interior of said casing'and which'passes under said 'shelland between it and said cas.-

in and transversely of said screw threads, sald shell constituting anupper wall and said casing a lower wall of said passage, said passage aving an outlet exteriorly of said casing, and the inner screw-threaded surface of saidmetal shell being exposedto the gas in said passa e.

5. An 'el ectric fuse having an enclosing` casing, a metal shell on the end of said casing, a fuse engaging A member engaged with said shell, `and aventing passage which is in c communication with the interior of said casing and which passes under said l`shell and between it and said casing, said shell constituting an upper wall and said casing a lower wall of said passage, saidv passage having an outlet exteriorly of the casing, said metal shell being internally corrugated and the corrugations thereof traversing and being exposed to the gas in said passage. v'

6. An electric fuse having an enclosing casing, an internally screw threaded metal shell receivedon the end of @said casing, a fuse engaging member engaged with said shell, Aand a venting passage located between said shell and said casing and being inv communication with the interior of said casing and having an outlet exteriorly of said casing, said shell constituting an outer wall and said casing constituting an inner wall of said passage and the internal screw threads of said shell traversing saidv passage.

7. An electric fuse having an enclosing casing, an externally screw threaded capholding shell located on theend of said cas.- in and a vent passage which extends long1- tu inally of the casing under said shell vand has inlet and outlet openings on opposite sides thereof.

8. An electric fuse having an enclosing casing, an externally screw threaded capholding Shelli.` located on the end of said casing, and a vent passage which extends longiwall and said casing constituting the bottom wall of said passage and said shell being exposed to the gas 1n said passage."

Q.An electric fuse'having an enclosing casing 'formed with a longitudinally extended venting passage at one endof its periphery, a *metal shell carried by the "end of the casing and overlying the major portion of said passage, and a fuse engaging member enclosing the-end of said casing and` said shell, said passage having an entrance into the interior of said member under said shell osing ex ma j screw on f 'aslot which extends,

sere threads and has a bottom wall which;

' and'havin an outlet betweenthe-other end of said she I and said casing.l l

10. Anfelectric fuse :having a tubular casjing, an exteriorly screw threaded metal shell -5 surrounding the end of and carried by said ca'sing,'anv end cap screw threaded onto said shell, and a venting passage extended longitudnally of said. casing under said shell and having communication with-the interior of 1Q- said end'cap and having an outlet exteriorly -of said casing.

11. An electric fuse havin 'casinil provided with a venting. slot in the perip eral end portion of said casing that is l5, extended longitudinally of the casing, an lext'eriorl screw threaded .metal ferrule that is carri by the end of said casingand overlies said slots and an end cap that is screw threaded onsaid shell, said slot having -an imv entrance that communicates with the interior ofjsad end cap` and having an outlet that is open exteriorly of saidcasing.

' 12.*'An1electric fuse having an enclosin external screw threads on the end o lfsaid casing, a venting' slot whichv is extended longitu'dinally of sald casing through said an enclosing screw threads and below the roots of said f metal shell having external screw `internal screw threads which "f ,received on-the screw threads ofl said l`saidshe'll 'constituting the top wall slot,l and an end cap screw threadedscrew threadsof said shell saidslot having anlcntrance lin the interior of saidend and having an outlet exteriorly ofsaidcesmgelectric fusehavingl air-'insulating the'end ofsaidcasln g 'tudina1lyi. ofsa1d casing across said! is located below the roots of said an internally. andfemrnany. mw threaded metal'. ferrule ha its screw' engaged v wi `.th`e (`eirternal screw threads of sal casing; said metal shellcrmf` stituting' thetop wall of--saidslotand hav] f its internal screw threadstra e sal slotwith thefapexes-thereof termina f close tot to 'the will' of said alot; and? an end "cap .screw threaded on s'aidvshell, said slot l 5- having an entraneein the interior of said end: cap and an` outlet exteriorly of said casing beyond` saidfshell.

14. An electric -havi an enclosing casing provided with vexterna screw threads 'on the end thereof, a vslot which extends lon gitudinally through said screw-threads and has a bottom wall which. `i s below the 0. roots of said threads, .a v in :etsl'shellhaving external screw threadsjand internalscrew threads thatare engagedfwith the vscrew dsofsaid -fcs ing its. internal screw threads rotation.

Leraars the gas in saidslot, and the apexes of said said slot, and an end cap screwthrea ed on the external screw threadscfl said shell, said slot having an entrance that communicates with the interior of said cap and an outlet exteriorly of said casing.

15. In an electric -fuse, a tubular enclosingl casing1 of insulating material having `an externa y screw-threaded end portion and an annular peripheral groove between the body of the casing and said screw threaded por-l tion, and a metal cap-holding shell having external screw threadsland internal screw threads. that are engaged with thev screw threads of said casing and havingan annular unthreaded end portion that is'located in saidgroove. and engages op 'te walls thereofA and constitutes means -w ich' cooperates with said screw threads in retaining said shell",

against rotation on said 16. In an electric fuse, a tu ular insulating enclosing'casing having an externally screw threaded end rtion and an endless annular groove which 1s sunk into the'casing adjacent the screw threads, a metal .capholdin shell having external cap-receiving screw reads and internal screw threads which engage the' external screw threads ofsaid' casing1 and. also having aA part which is sunk-"into said grooveand closely engagesthe opposite walls Ithereof andA cooperatesr `with sa1d engaged screw threadsin holding said shell :against 17. In an electric/fuse, a-tubular enclosrilgA .casing of insulatin material havingexte screw threadson e end of the casing,fa.pei ripheral annular oovedocated'at the end of'- sard screw threa threads and` thebody of the"casing,.and a metal shell'having external `screw th and internal screw threads thatare engaged with the'screw threads offsaid casing, 4an 11n- `threaded' annular end portion which is" ceived in said groove andwhichcooperates with said screw threads in' holdingfsaid shell` against rotation on saidcasing.

of insulatin material having'external screw' 'threads on t e end of the casin and a peripheral annular groove located and between said screw 18. In an electricrfuse, an enclosing screw threads and the body of the casing a nal and internal screw threads received inl the screw threadsof said casing and having an unthreaded end portion which is sunk into andclosel* engages 4with the -wall of saidgroove cooperates withsaid screw headsf to hold said shell against rotation.

19;. an electric fuse, an enclosing casing-V of' insulating material having external screw4 thin vmetal shell having'l complemental exter` tween said "f threads on the end of the casing, and a peripheral annular groove located between said screw threads and the body of the casing, a thin metal shell having complemental exter- 5 nal' and internal screw threads receivedin the screw threads of said casing and having an Unthreaded end portion which is sunk into and closelyr engages with the wall of said groove and cooperates with said screw lthreads to hold said shell against rotation, said shell also having spurs which are sunk into said casing.

20. In an electric fuse, an enclosing casing, and venting means therefor comprising a metl'al-member which surrounds said casing and has a corrugated inner surface that confronts and is closely spaced from the outer periphery Vof said casing, the spaces between two corrugations constituting expansion chambers,

` and means to conduct gases from the interior of said casing in series through said eXpansion chambers and thence to the atmosphere.

21. An electric fuse having an enclosing casing, a metal shell on the end of said casing, a fusible element within said casing, a fuseengaging member engaged with said shell, and a venting passage which is in communication with the interior of said casing and which passes under said shell and between it yand said casing and has an outlet exteriorly of said casing, said 'shell constituting an upper wall of said passage and the inner surfaces of said shell being exposed to the vapors of said fusible element in said passage when said fusible element melts, said shell being composed of a metal having a melting temperature that is higher than the vaporizing temperature of said fusible element so that it cannot be melted by the hot vapors of the fusible element at the time the fuse operates.

FRANKLIN N. CONANT. 

